Functional tester for printed circuit boards, and associated systems and methods

ABSTRACT

Systems and methods for testing printed circuit boards (PCBs) are disclosed herein. In one embodiment, a tester for printed circuit boards (PCBs) includes a test fixture having a plurality of electrical contacts for contacting the PCBs that are units under test (UUTs). The test fixture carries a remote test peripheral master (RTPM) module, and a remote test peripheral slave (RTPS) module. The RTPM module and the RTPS module are connected through a remote test peripheral (RTP) bus.

CROSS-REFERENCE TO RELATED APPLICATION

This application is continuation of U.S. application Ser. No.16/485,149, filed Aug. 9, 2019, which is a national phase applicationunder Sec. 371 of International Application No. PCT/US2018/017550, filedFeb. 9, 2018, which claims priority to U.S. Provisional Application No.62/457,593, filed Feb. 10, 2017, which disclosures are incorporatedherein by reference.

BACKGROUND

Printed circuit boards (PCBs) are tested before being shipped tocustomers. PCBs typically include internal routing (traces) distributedover several metallization layers. The horizontal metallization layersare electrically interconnected by vertical vias. Electrical components(resistors, capacitors, integrated circuits (ICs), connectors, etc.) areattached to pads at the surface of the PCB or to the metallization ofthrough-holes extending vertically through the thickness of the PCB.These electrical components are interconnected by the traces of the PCB.The external connections of the PCB are typically edge connectors orother connectors carried by the PCB.

The PCB and the electrical components are sometimes collectively calleda printed circuit board assembly (PCBA). Generally, the terms PCB andPCBA are used interchangeably, i.e., the term PCB can denote the boarditself, as well as an assembly of the board and the electricalcomponents that are carried by the board.

Testing of the PCBs (or the PCBAs) can be in-circuit (in-circuit test orICT) or functional (functional test or FT). In-circuit test performs a“schematic verification” by testing individual components of the PCB oneat a time. For example, resistance, voltage drop, polarity, etc., of theindividual electrical components are measured and compared againstexpected values for that component. Typically, the in-circuit test isnot done “at speed,” and does not verify interoperability of theelectrical components. However, the in-circuit test can still beeffective in finding manufacturing defects of the PCB, the electricalcomponents, or the defects in the attachment of the components to thePCB. For example, the in-circuit test may detect solder shorts, missingcomponents, wrong components, improperly attached components (e.g., adiode that is rotated 180°), or open connections. Most of the in-circuittests are performed without the PCB being powered, thus avoiding theconditions that could damage components. Test programming effort can beminimized as the programming consists of switching the test instrumentsto connect to the PCB via a bed-of-nails (BON) fixture.

Functional testing is designed to assure that circuitry functions withinthe specifications. Such testing may be done “at speed” through the PCBconnectors (e.g., edge connectors on the PCB) and/or the BON fixture.Functional tests can identify functional defects within the PCB as wellas the defects in the components. For example, functional test mayassess functionality of the PCB while applying marginal power supplyvoltage and/or current to an IC to assess functionality of the IC, maydetermine power consumption of the PCB or a component on the PCB duringoperation, may test operation of the components at their specificationfrequency, etc.

However, the test programs for functional test require a thoroughunderstanding of the device under test (DUT) performance, thusprogramming costs are typically higher than those for the in-circuittest. Furthermore, with conventional BON systems, the programming has tobe repeated for every new PCB design, because the pins of the BON (e.g.,pogo pins) are wired back to the corresponding pins of the instrumentsin the PCB testers, and the instruments must be reprogrammed for thenext PCB design. Additionally, some high frequency tests may not bepossible due to relatively large distance from the instruments in thePCB tester to the PCB under test (also referred to as “unit under test”or UUT). This relatively large distance may cause significantattenuation of the signals in the cables that run from the mainframe tothe UUT. Accordingly, systems and methods for improved in-circuit testand functional test are needed.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of theinventive technology will become more readily appreciated and betterunderstood by reference to the following detailed description, whentaken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a partially schematic, isometric view of a PCB tester inaccordance with prior art;

FIG. 2 is a partially schematic view of a test fixture in accordancewith prior art;

FIG. 3 is a block diagram of a PCB tester in accordance with anembodiment of the present technology;

FIG. 4A is a block diagram of a PCB tester in accordance with anembodiment of the present technology;

FIG. 4B shows detail A of FIG. 4A;

FIG. 4C is a partially schematic isometric view of a PCB tester inaccordance with an embodiment of the present technology;

FIG. 4D is a schematic view of RTP module mounting holes in accordancewith an embodiment of the present technology;

FIG. 5 is a block diagram of RTP master (RTPM) and RTP slave (RTPS)chain in accordance with an embodiment of the present technology;

FIG. 6 is a block diagram of connections between a control system and atest fixture in accordance with an embodiment of the present technology;

FIG. 7 is a block diagram of connections among RTPM and RTPS modules inaccordance with an embodiment of the present technology;

FIG. 8 is a block diagram of an RTPS module in accordance with anembodiment of the present technology;

FIG. 9 is a block diagram of an RTPM module in accordance with anembodiment of the present technology; and

FIG. 10 is a block diagram of an RTPS module in accordance with anembodiment of the present technology.

DETAILED DESCRIPTION

Specific details of several embodiments of the PCB testers are disclosedherein. The inventive technology relates to PCB testers that areconfigurable, and can perform functional tests on multiple PCBs inparallel. More particularly, the present technology relates to PCBtesters that are configurable, and can perform both in-circuit test(ICT) and functional test (FT) on multiple PCBs in parallel. Asignificant portion of the test electronics may be located on the testfixture itself (i.e., close to the PCBs under test, also referred to asunits under test or UUTs). As a result, signal/power path to the UUTs isshortened. In some embodiments, the tester may test multiple PCBs inparallel. These PCBs may have different configurations (e.g., differentdesigns).

In some embodiments, the test electronics may be distributed overmaster/slave modules (also referred to as remote test peripherals orRTPs). Several RTP master/slave module chains may be connected throughUSB link or other fast serial link to an universal serial bus (USB) hub,and further to a host controller (i.e., a computer or a server). The RTPmaster/server modules (RTPM/RTPS) in the chain can communicate through aserial link, for example, an 8-bit asynchronous serial link. TheRTPM/RTPS module chains can be reconfigured or reprogrammed depending onthe configuration and number of the UUTs tested in parallel, withouthaving to replace the RTPM/RTPS modules.

In some embodiments, the test fixture is “self-aware,” i.e., capable ofreporting its configuration back to the control system. For example, thetest fixture may report configuration of the RTP master/slave modules,number of the boards, assignments of the pin contacts, revision numberof the master/slave module, etc.

In some embodiments, the test program (also referred to as a testsequence) is loaded directly on the test fixture. For example, the testfixture may include memory chips for storing the test program and datafiles having the test point assignments.

A person skilled in the art will also understand that the technology mayhave additional embodiments, and that the technology may be practicedwithout several of the details of the embodiments described below.

FIG. 1 is a partially schematic, isometric view of a PCB tester 10 inaccordance with prior art. The PCB tester 10 includes a mainframe 13 anda test fixture 18. The conventional test fixture is typically built as amechanical “bed of nails” (BON) fixture that is specifically designedfor a particular layout of the UUT. The mainframe 13 includeselectronics that sends test vectors and power to a UUT 16. For example,the mainframe 13 can include test instruments 13 a for checkingopen/shorts on the UUT 16, and a power supply 13 b for poweringcomponents 22 on the UUT 16.

The test fixture 18 includes contact pins 20 (e.g., pogo pins) thatelectrically connect electronics in the mainframe 13 with traces 21, andfurther with components 22 of the UUT 16. Additional electricalconnectivity between the test fixture 20 and the UUT 16 is providedthrough a cable 17.

Test cables 14 connect the test instruments and power supplies of themainframe 13 with the test fixture 18. A host computer 11 controls theoperation of the mainframe 13 (e.g., sending the test vectors throughthe cables 14) and interprets the results of the test (e.g.,presence/absence of defective components on the UUT 16). However, arelatively long length of the test cables 14 can degrade signalintegrity due to noise and transmission line effects, especially for thehigh frequency testing.

FIG. 2 is a partially schematic view of a test fixture in accordancewith prior art. The test fixture 18 can include an assembly of plates 18a and 18 b for improved vertical alignment of the contact pins 20. Themainframe tester 13 provides test vectors and/or power through testcables 14. In operation, the contact pins 20 make contact with thecomponents 22 or the traces of the UUT 16 to provide electricalconnectivity to/from the mainframe tester 13. After completing thetesting of the UUT 16, the tested UUT is removed and the next UUT isloaded to make contact with the test fixture 18.

FIG. 3 is a block diagram of a PCB tester 100 in accordance with anembodiment of the present technology. The PCB tester 100 includes a testfixture 118 and a control system 120.

In some embodiments, the control system 120 includes an ICT (in-circuittester)/MDA (manufacturing defects analyzer) 112 and a host computer(host controller) 111. The control system 120 may also be referred to asthe ICT/MDA system 120. A host computer 111 provides an operatorinterface for communicating with the ICT/MDA system 120 through a bus121, which may be a USB connection or other high speed serial bus.

The test fixture 118 can be connected with the control system 120through one or more high speed serial buses 122, for example USB buses.In addition to the control/test signals received from the control system120, the test fixture 118 may generate test signals and power forfunctional test (FT) of the UUTs 117 through one or more RTPM/RTPSchains 161/162 carried by the test fixture. The test fixture 118 can beconnected to a UUT panel 116, which includes one or more PCBs 117 (UUTs117).

In operation, the ICT may, for example, detect opens/shorts on the UUTs117, and the MDA may evaluate manufacturing defects of the UUTs 117.Some examples of the ICT tests in combination with the functional test(FT) are described below.

RTPM/RTPS Chains Carried by the Test Fixture

In some embodiments, much of the electronics for the functional test(FT) resides within the test fixture 118, therefore minimizing thenumber of test cards in the control system 120. The FT hardware of thetest fixture 118 can include one or more RTP master (RTPM) modules 161,each controlling one or more RTP slave (RTPS) modules 162-i. The RTPSmodules can perform a variety of tasks including, for example, powerregulation, load switching, current/voltage sensing, UCT (universalcounter/timer), logic analysis/playback, LED optical testing, RF (radiofrequency) testing, HIPOT (high potential) testing, relay control, andcustomer-specific functions.

Furthermore, the RTP bus 165 (for example, a universal asynchronousreceiver-transmitter or UART) can support a relatively simple additionof the RTPS module, therefore enabling expansion of the functional testsas required by different number of UUTs 117 from one test to another. Inmany embodiments, the number of RTPM/RTPS chains and the composition ofthe RTPS modules can be changed to suit a specific test or a specificUUT. As a result, the tester is modular, scalable and customizable.

In some embodiments, RTPM/RTPS modules are programmable. Therefore, themodules can be reconfigured to test different UUTs (through, forexample, Command Descriptors and Pin Information) or reprogrammed withdifferent firmware without replacing the RTPM/RTPS modules. Furthermore,since the RTPM/RTPS modules are carried by the test fixture 118, changesof the control system 120 can be minimized for differentconfigurations/numbers of the UUTs 117.

In operation, the RTPS modules can communicate with UUTs through buses221, e.g., CAN (controller area network), LIN (local interconnectnetwork), I²C (inter integrated circuit), I²S (inter integrated sound),JTAG (join test action group), SPI (serial parallel interface), UART(universal asynchronous receiver-transmitter), etc. Stated differently,the RTPM module establishes a control channel over the RTPS modulethrough the RTP bus 165. These bus communication protocols can support avariety of RTPMs/RTPSs having different test capabilities. Generally,the UUTs 117 that are being tested in parallel have the same design.However, in some embodiments, the UUTs having different designs may betested simultaneously through a single fixture by differentlyprogramming the RTPM/RTPS modules that interface with different UUTdesigns.

In many embodiments, tester quoting process is simplified for the testerthat has modular RTPM/RTPS design. For example, the test fixture 118that carries standardized RTPM/RTPS modules 161/162 is generally easierto quote than a custom-designed test fixture 118 having the samecapability. Furthermore, quoting the test fixture 118 that carriesstandardized RTPM/RTPS modules 161/162 can be more precise.

Test Program and Test Pin Assignments Pre-Loaded on Test Fixture

Conventional FT systems reserve a block of testpoint numbers which maynot correspond to the testpoint numbers that the tester instruments areactually connected to. Therefore, additional knowledge is required toconnect the wires of the tester to the testpoints of the UUTs. In someembodiments of the inventive technology, the testpoint information maybe stored with the test program (the test sequence) directly on the testfixture 118, for example, on a memory storage device 167 (e.g., flashmemory, EPROM, etc.) of the test fixture 118. The testpoint informationmay be used for the functional test programs and to simplify wiring ofthe fixture 118. The testpoint information may assist withauto-generation of a netlist template, which the user can use to fill inappropriate testpoint information for the fixture. Furthermore, thetestpoint information can be used for generating wiring instructions,fixture hardware diagrams and/or for self-test of the RTPM/RTPS moduleson the test fixture.

In some embodiments, the UUTs 117 are tested in less time because thecommunication between the control system 120 and the test fixture 118 isminimized (e.g., no need to transfer the listings of the testpoints fromthe control system 120 to the test fixture 118). In operation, the testresults may be aggregated for several UUTs 117, and then collectivelysent to the control system 120 over the high speed serial bus 122 tofurther minimize data transfers between the control system and the testfixture.

Self-Aware Test Fixture

In some embodiments, the RTPM module 161 can perform a system query to,for example, determine the number and type of the RTPS modules 162 inthe RTP fixture. The system query may also determine particularaddresses of the RTPM/RTPS modules, and the corresponding features thatspecific RTPM/RTPS module support. These capabilities enable the testfixture to be self-aware.

In some embodiments, the RTPS modules 162 also include commands. Forexample, an RTPS module 162 may include a default set of commands, whichcan be used for querying information pertaining to each module (e.g.,board information, pin information, command descriptions, etc.),therefore allowing the RTP fixture 118 to be self-discoverable. Forexample, information stored in RTPS modules 162 may allow the user orother modules 161/162 to:

-   -   download board information (part number, revisions,        descriptions);    -   download information related to number of channels supported by        the RTPS module, and    -   download information about the supported features and commands.        This information may provide full command descriptors, and may        be sufficient for the user to know the required parameters,        expected return values, and the effects of any command supported        by the RTP module. Furthermore, the information may be used by        the control system 120 to display to the operator the        appropriate graphical interface for setting up RTP tests.

Self-Diagnostics of RTPM/RTPS Modules

In some embodiments, the RTPM module 161 and/or RTPS module 162 maycarry hardware that enables the microcontroller to perform self-testdiagnostic tests of on-board circuitry to detect issues with theRTPM/RTPS modules (e.g., erroneous wiring, hardware failures, powerissues, etc.). Some examples of self-tests executed by the RTPS module162 are:

-   -   on-board diagnostic programs. Software may be provided which        allows the microcontroller to detect problems on the RTPM/RTPS        without external help;    -   user-coordinated diagnostic programs. These self-test programs        may require the assistance of an operator to provide a stimulus        to a testpoint using a ground probe or some other tool; and    -   ICT/MDA-coordinated diagnostic programs. The ICT/MDA may either        provide stimulus to the outputs of the RTPS module, or take        measurements of the RTPS module outputs.

FIG. 4A is a block diagram of a PCB tester in accordance with anembodiment of the present technology. The illustrated PCB tester 100includes the control system 120 and the test fixture 118. Signals/powerfrom the test fixture 118 to the UUTs 117 can be routed through contactpins 20, optical connections 26, solenoids 28, and/or wirelessly. Insome embodiments, the control system 120 is connected to the testfixture 118 through a transfer block 220 (e.g., paired connectorssuitable for high speed signals).

In some embodiments, the RTPM module 161 serves as a master device inthe RTP bus chain, the RTPS modules 162 being attached-to andcontrolled-by the RTPM module 161. In some embodiments, during thepower-on sequence for the test fixture 118 or when a bus reset isrequested, the RTP modules undergo an auto-addressing phase toautomatically detect how many RTPS modules 162 are included in the RTPchain, and what their respective positions are within the chain.

In some embodiments, the per-channel circuitry of the RTPS module isduplicated for each channel supported by the RTPS module. The channelsof the RTPS module may be capable of operating independently from oneother. The microcontroller firmware of the RTPS module maydisable/enable the independent channels, or certain features could beapplied to one enabled channel and not others. In some embodiments, theRTPS modules are capable of simultaneous (i.e., parallel) functionaltesting of multiple or all UUTs 117, therefore increasing the throughputof the PCB tester 100.

Shortened Distance Between Test Fixture and UUTs

With the conventional testers, a relatively long distance between thesources of the signals and the UUTs limits the signal frequency and/orpower available for testing the UUTs. In some embodiments of the presenttechnology, for example with high-speed testing of the UUTs 117, asignal sources on the RTPS modules 162 are located closer to the UUTs117, therefore reducing issues that are caused by long transmissionlines (e.g., degraded signal integrity).

The RTPS modules 162 may be designed to interface with and test multipleUUTs 117 connected to a channel (also referred to as a “data channel”).For example, the individual channels of the RTP module 162 may utilizeone or more contact pins 20, optical connections 26, solenoids 28,and/or wireless connections to transfer signals to/from the UUTs 117. Inmany embodiments of the present technology, the distance between theRTPS modules 162 and the UUTs 117 is shortened because the RTPM/RTPSmodules are carried by the test fixture 118.

Combined ICT/FT Test

In some embodiments, the tester 100 is configured to execute both theICT and the FT. For example, for the ICT test, the ICT/MDA 112 can bewired directly through traces 222-1 to some of the contact pins 20.Other pins 20 in the ICT test may be connected to the ICT/MDA 112through traces 222-2 and relays 240 of the RTPS modules 162. The relays240 may be, for example, electromechanical or solid-state relays (e.g.,banks of transistors). The relays may switch the UUTs 117 from ICT test(UUT test points directly connected to ICT/MDA 112) to functional test(UUT test points connected to the circuitry of RTPS 162), and viceversa.

In many embodiments, when ICT and FT are combined into one tester 100,the test flow is simplified and accelerated. Furthermore, if the ICTfinds problems (e.g., shorts on the UUT), then the select relays mayswitch to isolate particular parts of the FT circuitry on the RTPS 162,therefore preventing damage to the RTPS modules 162.

Buses Connecting RTPM

In some embodiments, the RTPM 162 may be in communication with thecontroller 111 through a bus 122-1 (e.g., high speed serial bus) and incommunication with the ICT/MDA 112 through a bus 122-2 (e.g., a serialor parallel bus, also referred to as a handshake connection). In someembodiments, the handshake connection 122-2 may be a parallel bus. Whenexchanging small amounts of data between the ICT/MDA system 120 and theRTPM 161, the handshake connection 122-2 may be more agile and fasterthan a nominally faster USB bus.

The RTPM 161 may also include one or more operational amplifiers (OPAMP) and analog to digital converters (A/D). The OP AMPs and A/Ds may beconnected to the ICT/MDA 112 through an analog bus 122-3. For somerelatively slow-speed UUT tests, for example, a DC test, the bus 122-3may connect the A/D of the RTPM module to the UUTs through a bus 221-1(also referred to as “conventional ICT wiring”), or through a bus 221-2(also referred to as “MDA wiring”) and further through the relay bank240 and a bus 221-3 (also referred to as “UUT wiring”).

Verification of Connectivity Between RTPS Modules and ICT/MDA

FIG. 4B shows detail A of FIG. 4A. In particular, the relay 240-i mayconnect the UUT 117 to either the RTPS module 162-i for the FT or to theICT/MDA 112 for the ICT. In some embodiments, a resistor 242 is added inparallel with the relay's path to the ICT/MDA 117 to isolate the FTpoints from the loading capacitance of the wires coming from the ICT/MDA112 (the wires of the bus 221-2). Additionally, a voltage drop can bemeasured from the UUT 117 to the ICT/MDA 112 even when the relayconnects the UUT 117 with the RTPS 162. As a result, in at least someembodiments, the ICT/MDA 112 can determine if the connection from theRTPS to the UUT functions properly (e.g., no opens in the path). In manysituations, in absence of the resistor 242, determination about theintegrity of the connection from the RTPS to the UUT must be performedmanually, resulting in higher cost and longer fixture development/debugtimes.

Vertically Stacked RTPM/RTPS Chains

FIG. 4C is a partially schematic isometric view of a PCB tester inaccordance with an embodiment of the present technology. In someembodiments, the test fixture 118 carries the RTPM/RTPS chain that isvertically stacked. For example, the RTPM module 161 may support one ormore RTPS modules 162 in a vertical stack. The uppermost RTPS module 162in the stack contacts a test interface 119 that supports the UUTs 117.In some embodiments, the contact pins 20 of the test interface 119 touchthe test points of the UUTs 117 to establish electrical connectivity.The electrical connectivity may be established with mechanical pins,optical contacts, solenoids, or wireless connections. In someembodiments, vertical stacking of the RTPM/RTPS chain results in a morecompact test fixture. Furthermore, a reduced distance between the RTPSmodules and the UUTs decreases signal/power degradation because of theshortened electrical path from the RTPS modules to the UUTs.

FIG. 4D is a schematic view of RTP module mounting holes in accordancewith an embodiment of the present technology. In some embodiments, theRTPMs and RTPSes may include a standardized distribution of mountingholes 172. For example, the rows and columns of the mounting holes 172may be separated by standardized widths W and heights H. Suitablestandoffs may maintain vertical offsets between individual RTPM/RTPSmodules.

FIG. 5 is a block diagram of RTPM/RTPS chains in accordance with anembodiment of the present technology. The illustrated RTPM/RTPS chainsare individually connected to a fast serial hub 168 through a high speedserial bus 122A, and further to the control system 120 with a high speedserial bus 122B. In some embodiments, the high speed serial buses122A/122B are USB buses. Multiple RTPM/RTPS chains in parallel may allowfor a higher data throughput. For example, conventional functional testsare performed on one UUT at a time. As a result, with the conventionalsystems, time required to test the entire batch of the UUTs 117generally corresponds to the time required for testing an individual UUTmultiplied by the number of UUTs 117 in the UUT panel 116. In someembodiments of the present technology, a single RTPM/RTPS chain 161/162can test multiple UUTs 117 in parallel. Additionally, multiple RTPM/RTPSchains may further increase the parallelism of the test. As a result,multiple UUTs 117 can undergo the same FT in the same time as it takesfor one UUT 117. Such a capability may be useful for the test processeshaving strict takt time requirements.

In some embodiments, multiple RTP master/slave chains 161/162 canfurther increase throughput when, for example, the number of UUTs 117 isincreased. For example, in some tests three RTPM/RTPS chains 161/162 maybe configured to support testing of three UUTs in parallel. When afourth UUT 117 is added to the parallel test, the resources of theexisting three RTPM/RTPS chains 161/162 may be reconfigured to supporttesting of the fourth UUT without having to add additional RTPM/RTPSchains. In contrast with the embodiments of the inventive technology,the addition of another UUT requires adding dedicated test resources toconventional PCB testers.

In some embodiments, the test fixture 118 includes the memory storagedevice 167 for storing test programs, test pin assignments, testvectors, and/or other data for testing the UUTs 117. In someembodiments, the test fixture 118 communicates with the ICT/MDA 112through the host controller 111.

FIG. 6 is a block diagram of connections between the control system 120and the test fixture 118 in accordance with an embodiment of the presenttechnology. In some embodiments, the control system 120 includes a relayswitching matrix 241 that may be a solid relay switching matrix (e.g., abank of transistors). Depending on the isolation requirements of thetestpoints on the UUTs 117, the relay switching matrix 241 may connectthe testpoints on the UUTs 117 to the RTPM/RTPS chain 161/162 withoutisolation or with isolation. For example, the relays may be closed todirectly connect the testpoints on the UUTs 117 with the ICT/MDA 112 forthe ICT (e.g., testing opens/shorts, resistance measurements, etc.).Analogously, the UUT testpoints that are used in conjunction with FT mayrequire isolation or local switching. In some embodiments, the testfixture 118 includes in-system programming (ISP) hardware, for exampleISP controller and/or ISP buffers. In some embodiments, the ISP hardwaremay include MultiWriter.

In some embodiments, the test fixture 118 may include RTPS modules 162that include the functionality of power control (e.g., the RTPS 162-1)or analog divider (e.g., the RTPS 162-2). In some embodiments, the testfixture 118 includes RTPS modules with other functions, for example:

-   -   serial communication protocols (CAN, LIN, I²C, I²S, JTAG, SPI,        UART, etc.);    -   power regulation (buck/boost regulators, linear regulators, load        switches, discharge modules, function generators);    -   data sampling (frequency/timing, logic recording/playback);    -   optical applications (LED sensing, infrared        transmission/detection, fiber optics);    -   power detection (DC/AC voltage/current sensing, HIPOT); and/or    -   solenoid/relay control.

FIG. 7 is a block diagram of connections among RTPM and RTPS modules inaccordance with an embodiment of the present technology. The RTPM/RTPSmodules 161/162 may be carried by the test fixture 118 (not shown). Insome embodiments, the RTPM/RTPS modules 161/162 have their upstreamports connected (“chained”) to the corresponding downstream portsthrough RTP bus 165. For example, a downstream transmitter node TXD ofthe RTPM module 161 may be chained to an upstream receiver node RXU ofthe RTPS module 162-1. As another example, a downstream receiver nodeRXD of the RTPS module 162-1 may be chained to an upstream transmitternode TXU of the RTPS module 162-2. On the upstream end of the RTPM/RTPSmodule chain, the RTPM module 161 has only the downstream nodes TXD/RXDfor connecting with the rest of the chain. Analogously, on thedownstream end of the RTPM/RTPS chain, a termination may be added toshort the TXD to the RXD node of the RTPS module 162-2. In someembodiments, the RTPS module 162 may automatically detect which of thetwo ports is upstream or downstream, resulting in simpler chaining ofthe modules.

In operation, the RTPM module 161 may initiate communication over theRTP bus 165. In some embodiments, the RTPM and RTPS modules implement acommon communication protocol, whereby the RTPM module can select andinitiate commands, and transfer data to one or more RTPS modules. Forexample, the RTPM module 161 may communicate to the RTPS modules 162 toobtain information about the RTPS modules: the module board number andboard revision, build revision number, communications driver versioninformation, descriptions, and usage information about any of thesupported command handler functions (parameter data, return data), andinformation about the number of output channels and respective headerpins. The RTPM module 161 may also control the RTPS modules 162 to:modify communications settings, download error reporting information forRTP bus communication errors, perform a soft reset of the RTPS module,read from the device memory, manipulate the device memory, etc.

In some embodiments, the RTP bus is an 8-bit asynchronous serial bus.When the RTP modules are powered on, the RTPM module 161 may initiate asynchronization phase, during which the RTPS modules 162 aresynchronized to the bus 165. The synchronization phase can force alldevices on the RTP bus 165 into the same communication state. When thisphase is completed, the RTPS modules 162 can start accepting commandpackets from the RTPM module 161, thereby the internal functions of theindividual RTPS modules 162 become available to the RTPM module 161 andthe controller 111.

In some embodiments, each RTPS module 162 includes two 2-bitmultiplexers MPLX for outputting upstream TXU and downstream TXDsignals. The multiplexers MPLX may be controlled by the signals TXD_ENand TXU_EN. Depending on the state of these two signals, the RTPS can bein one of the four modes described in Table 1 below.

TABLE 1 Communication modes based on multiplexer states TXD_EN TXU_ENMode Description 0 0 Pass-through Mode The module is disabled fromcommunicating upstream or downstream. The micro can still listen formessages coming from upstream or downstream. 0 1 Privileged upstream Themodule can transmit upstream mode towards the RTPM, however cannottransmit downstream. 1 0 Privileged downstream The module can transmitdownstream, mode however cannot transmit upstream. 1 1 Full privilegedmode The module can transmit both upstream and downstream.

FIG. 8 is a block diagram of the RTPS module 162 in accordance with anembodiment of the present technology. With the illustrated embodiment, amicrocontroller MICRO is directly connected to fewer points on bus 165,because the microcontroller MICRO is not connected to the RXD and TXDports any more. Instead, the RXD and TXD ports are connected to themultiplexers MPLX.

FIG. 9 is a block diagram of an RTPM module 161 in accordance with anembodiment of the present technology. In some embodiments, the RTPMmodule 161 includes several inputs/outputs: analog input bus, USB inputand handshaking signal port at its upstream side, and RTP bus TX/RXports, flag (FLAG) and reset (RESET) ports on its downstream side.

The RESET port may drive a hard reset of the RTPS boards. In response,the RTP hardware is configured into a known reset state. The FLAG portmay be pulled up by the RTPM module 161, and may be programmed as aninterrupt request (IRQ) pin for coordinating tasks between RTPM/RTPSmodules. In some embodiments, the FLAG pin also provides a conduit ofpassing control of RTPS module features to other electronics of the testfixture 118.

The RTPM module 161 may also include a general purpose input/output(GPIO) header 231 to provide access directly to port pins on themicrocontroller MICRO. In some embodiments, the GPIO header 231 may beused for controlling in-fixture signals. In other embodiments, the GPIOheader may be used for connections directly to the contact pins.

In some embodiments, the analog input port of the RTPM module 161 can bean 8-channel analog input port. For example, the analog input port maybe configured to measure differential voltages or single-supplyvoltages.

In some embodiments, the RTPM module 161 is connected to the controlsystem 120 via the USB port. The USB port may also provide power to themodule.

Hardware Scan

On initialization, the RTPM module 161 may synchronize the RTPS modules162 and may perform a full hardware scan of the devices contained on theRTP bus. The RTPM module may also collect information about the modulepart numbers, supported commands, and pin information, which can bestored in a memory (e.g., the memory storage device 167).

In some embodiments, the stored information may be used to check againsttest programs, and can be used to detect proper hardware configurationand proper functions of the test fixture 118. Furthermore, the RTPMsoftware may store a hash of the RTPS in-memory data, to be used toverify that the test fixture 118 includes the proper hardware andfirmware during the run of any test program.

In some embodiments, the hardware scan compares configurations of theRTPM/RTPS modules in the fixture to the hardware listing in thespecification file. In general, if differences between the real andexpected hardware configurations are detected, the scan fails. Thehardware scan may also provide a list of detected hardware differencesto the operator. In some embodiments, an operator may load descriptionof the expected hardware from a file. In some embodiments, the detectedhardware configuration is saved as a hardware descriptor in a dedicatedfile.

FIG. 10 is a block diagram of an RTPS module 162 in accordance with anembodiment of the present technology. In some embodiments, the RTPSmodule 162 may be powered from a DC power supply using, for example, a12V power connector. Additionally, the RTPS module 162 may includeDC-to-DC converters to provide power for the on-board electronics. Theoperation of the upstream and downstream port connectors, the RESET pin,and the FLAG pin may be similar to those described with reference toFIGS. 8 and 9 .

In some embodiments, the RTPS module 162 includes module-specificcircuitry that is tailored for each RTPS variant to facilitate specificfunction of that module (e.g., output buffers, voltage translators,transceivers, etc.). The RTPS module 162 may include multiple testchannels (Ch1 TPs, CH2 TPs, etc.) for testing one or more UUTs 117. Insome embodiments, the circuitry on the RTPS module 162 is duplicated foreach test channel supported. The contact pins 20 may be assigned to theindividual test channels (Ch1 TPs, CH2 TPs, etc.) of the UUT.

In some embodiments, the RTPS module 162 may use a communications driverto control an upstream and downstream TX/RX ports, and process telegramstransmitted over those ports. The RTPS module 162 may also control itsown functions, for example, control an SPI or I2C device, turn on or offtimer or pin edge/level detection interrupts, toggle various GPIO pinshigh or low, read the states of GPIO pins or on-chip ADCs, coordinatemeasurements with other RTPS modules, reprogram the RTPS modulefirmware, and/or perform self-test routines.

From the foregoing, it will be appreciated that specific embodiments ofthe technology have been described herein for purposes of illustration,but that various modifications may be made without deviating from thedisclosure. Moreover, while various advantages and features associatedwith certain embodiments have been described above in the context ofthose embodiments, other embodiments may also exhibit such advantagesand/or features, and not all embodiments need necessarily exhibit suchadvantages and/or features to fall within the scope of the technology.Accordingly, the disclosure can encompass other embodiments notexpressly shown or described herein.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A tester for printedcircuit boards (PCBs), comprising: a test fixture having a plurality ofelectrical contacts for contacting the PCB s that are units under test(UUTs), wherein the test fixture carries: a remote test peripheralmaster (RTPM) module, and a plurality of remote test peripheral slave(RTPS) modules, wherein the RTPM module and the RTPS modules areconnected through a remote test peripheral (RTP) serial bus to form amaster/slave chain, and wherein the RTPM module is configured forcommunicating with the UUTs exclusively through the plurality of theRTPS modules of the master/slave chain, and wherein the plurality ofRTPS modules are configured to communicate through the RTP serial buswith the RTPM module of their master/slave chain only.
 2. The tester ofclaim 1, wherein the plurality of RTPS modules comprise a first RTPSmodule and a second RTPS module in communication with the first RTPSmodule.
 3. The tester of claim 2, wherein the RTPM module is a firstRTPM module, the first RTPS module belongs to a first plurality of RTPSmodules, and the RTP serial bus is a first RTP serial bus, the testerfurther comprising: a second RTPM module, and a second plurality of RTPSmodules, wherein the second RTPM module and the second plurality of RTPSmodules are connected through a second RTP serial bus, wherein the firstplurality of RTPS modules are configured for communicating through thefirst RTP serial bus with the first RTPM module only, and wherein thesecond plurality of RTPS modules are configured for communicatingthrough the second RTP serial bus with the second RTPM module only. 4.The tester of claim 3, wherein the first RTPM module and the firstplurality of the RTPS modules are vertically stacked in a first stack,and wherein the second RTPM module and the second plurality of the RTPSmodules are vertically stacked in a second stack.
 5. The tester of claim1, further comprising: a control system that is separate from the testfixture, wherein the test fixture is connected with the control systemthrough a high speed serial bus that is separate from the RTP serialbus.
 6. The tester of claim 5, wherein the control system comprises: anin-circuit tester (ICT), a manufacturing defects analyzer (MDA), and ahost controller.
 7. The tester of claim 1, wherein the RTP bus is an8-bit asynchronous serial bus.
 8. The tester of claim 1, furthercomprising at least one UUT electrically connected to the test fixturethrough a plurality of contact pins.
 9. The tester of claim 1, furthercomprising at least one UUT optically or wirelessly connected to thetest fixture.
 10. The tester of claim 1, further comprising a memorydevice configured to store test point information and test programs. 11.A method for testing printed circuit boards (PCBs) that are units undertest (UUTs), the method comprising: establishing a data channel betweenat least one remote test peripheral slave (RTPS) module of a pluralityof RTPS modules and at least one UUT of the UUTs; establishing a controlchannel between a remote test peripheral master (RTPM) module and theplurality of the RTPS modules of a master/slave chain through a remotetest peripheral (RTP) serial bus, wherein the RTPM module and the RTPSmodule are carried by a test fixture, and wherein the RTPM module isconfigured for communicating with the UUTs exclusively through the RTPSmodules of the master/slave chain, and wherein the plurality of RTPSmodules are configured to communicate through the RTP serial bus withthe RTPM module of their master/slave chain only; applying a testprogram to the at least one UUT; and collecting test data by the atleast one RTPS module, wherein the test data are generated in responseto applying the test program to the UUT.
 12. The method of claim 11,further comprising: controlling the plurality of RTPS modules by theRTPM module through the control channel.
 13. The method of claim 12,further comprising: comparing, by the at least one RTPS module, returnedtest data with expected return values, and based on comparing,determining a pass/fail condition of the UUTs.
 14. The method of claim11, further comprising: sending the test data to a host controller of acontrol system through a high speed serial bus that is separate from theRTP serial bus, wherein the control system is separate from the testfixture.
 15. The method of claim 14, wherein the test program executes afunctional test (FT), and wherein the data channel is a first datachannel, the method further comprising: establishing a second datachannel between: an in-circuit tester (ICT) and a manufacturing defectsanalyzer (MDA) of the control system, and the UUT; and running anin-circuit test on the UUT.
 16. The method of claim 11, furthercomprising: in response to a query from the RTPM module, reporting aconfiguration of the at least one RTPS module to the RTPM module. 17.The method of claim 11, further comprising: running a self-diagnosticsof the at least one RTPS module; and reporting the results of theself-diagnostics to the RTPM module.
 18. The method of claim 17, whereinthe results of the self-diagnostics of the at least one RTPS moduleinclude at least one of an erroneous wiring, a hardware failure, or apower issue.
 19. The method of claim 11, wherein the test program isstored on a memory storage device carried by the test fixture.
 20. Themethod of claim 19, further comprising initiating an execution of thetest program by the RTPM module.
 21. The method of claim 11, whereinmultiple UUTs are tested in parallel.
 22. The method of claim 21,wherein the UUTs have different designs.